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Abstract:

A method and a wireless power transmitter are provided for transmitting
wireless power to at least one wireless power receiver. The method
includes setting, by the wireless power transmitter, a search channel to
be used for communication with the at least one wireless power receiver;
detecting at least one of an energy level and a Received Signal Strength
Indication (RSSI) value of a signal received on the search channel; and
determining whether to designate the search channel as a communication
channel based on the detection results.

Claims:

1. A method of a wireless power transmitter for transmitting wireless
power to at least one wireless power receiver, the method comprising:
setting, by the wireless power transmitter, a search channel to be used
for communication with the at least one wireless power receiver;
detecting at least one of an energy level and a Received Signal Strength
Indication (RSSI) value of a signal received on the search channel; and
determining whether to designate the search channel as a communication
channel based on the detection results.

2. The method of claim 1, wherein determining whether to designate the
search channel comprises: determining whether the at least one of the
energy level and the RSSI value of the received signal is less than a
predetermined threshold; and designating the search channel as the
communication channel, when the at least one of the energy level and the
RSSI value is less than the predetermined threshold.

3. The method of claim 2, further comprising changing the search channel
to another channel, when the at least one of the energy level and the
RSSI value of the received signal is greater than or equal to the
predetermined threshold.

4. The method of claim 3, further comprising: determining whether there
is a remaining another channel, when at least one of an energy level and
an RSSI value of a signal received on the changed search channels is
greater than or equal to the threshold; and increasing the threshold,
when there is no remaining another channel.

5. The method of claim 4, further comprising: determining whether at
least one of an energy level and an RSSI value of a signal received on a
search channel is less than the increased threshold; and designating the
search channel as the communication channel, if the at least one of the
energy level and the RSSI value is less than the increased threshold.

6. The method of claim 1, wherein determining whether to designate the
search channel comprises: detecting at least one of an energy level and
an RSSI value of a received signal over each of a plurality of search
channels; and designating, as the communication channel, a search channel
from among the plurality of search channels having a smallest at least
one of an energy level and an RSSI value.

7. The method of claim 1, further comprising generating a network
Identifier (ID) of the wireless power transmitter based on a notice
signal received from another wireless power transmitter.

8. The method of claim 7, wherein the network ID is different from a
network ID of the another wireless power transmitter.

9. The method of claim 7, further comprising generating a notice signal
including the generated network ID, and transmitting the generated notice
signal.

10. The method of claim 9, wherein the notice signal further includes at
least one of protocol version information, a sequence number, information
about a wireless power receiver, and information about a number of
wireless power receivers in management.

11. The method of claim 1, further comprising determining a number of
other wireless power transmitters that use the search channel, based on
the detection results.

12. The method of claim 11, further comprising designating the search
channel as the communication channel, when the number of the other
wireless power transmitters that use the search channel is less than a
predetermined number.

13. The method of claim 11, further comprising designating the search
channel as the communication channel, when the search channel energy
level is less than a predetermined threshold, and the number of the other
wireless power transmitters that use the search channel is greater than
or equal to a predetermined number.

14. A wireless power transmitter for transmitting wireless power to at
least one wireless power receiver, the wireless power transmitter
comprising: a controller that sets a search channel to be used for
communication with the at least one wireless power receiver; and a
communication unit that receives a signal on the search channel; wherein
the controller detects at least one of an energy level and a Received
Signal Strength Indication (RSSI) value of the received signal, and
determines whether to designate the search channel as a communication
channel, based on the detection results.

15. The wireless power transmitter of claim 14, wherein the controller
determines whether the at least one of the energy level and the RSSI
value of the received signal is less than a predetermined threshold, and
designates the search channel as the communication channel, when the at
least one of the energy level and the RSSI value is less than the
predetermined threshold.

16. The wireless power transmitter of claim 15, wherein the controller
changes the search channel to another channel, if the at least one of the
energy level and the RSSI value of the received signal is greater than or
equal to the predetermined threshold.

17. The wireless power transmitter of claim 16, wherein the controller
determines whether there is a remaining another channel, when at least
one of an energy level and an RSSI value of a signal received on the
changed search channels is greater than or equal to the threshold, and
increases the threshold, when there is no remaining another channel.

18. The wireless power transmitter of claim 17, wherein the controller
determines whether at least one of an energy level and an RSSI value of a
signal received on a search channel is less than the increased threshold,
and determines the search channel as the communication channel, if the at
least one of the energy level and the RSSI value is less than the
increased threshold.

19. The wireless power transmitter of claim 14, wherein the controller
detects at least one of an energy level and an RSSI value of a received
signal over each of a plurality of search channels, and designates, as
the communication channel, a search channel from among the plurality of
search channels having a smallest at least one of an energy level and an
RSSI value.

20. The wireless power transmitter of claim 14, wherein the controller
generates a network Identifier (ID) of the wireless power transmitter
based on a notice signal received from another wireless power
transmitter.

21. The wireless power transmitter of claim 20, wherein the network ID is
different from a network ID of the another wireless power transmitter.

22. The wireless power transmitter of claim 20, wherein the communication
unit generates a notice signal including the generated network ID, and
transmits the generated notice signal.

23. The wireless power transmitter of claim 22, wherein the notice signal
further includes at least one of protocol version information, a sequence
number, information about a wireless power receiver, and information
about a number of wireless power receivers in management.

24. The wireless power transmitter of claim 14, wherein the controller
determines a number of other wireless power transmitters that use the
search channel, based on the detection results.

25. The wireless power transmitter of claim 24, wherein the controller
designates the search channel as the communication channel, if the number
of the other wireless power transmitters that use the search channel is
less than a predetermined number.

26. The wireless power transmitter of claim 24, wherein the controller
designates the search channel as the communication channel, when the
search channel energy level is less than a predetermined threshold, and
the number of the other wireless power transmitters that use the search
channel is greater than or equal to a predetermined number.

Description:

PRIORITY

[0001] This application claims priority under 35 U.S.C. §119(e) to
U.S. Provisional Patent Application Ser. No. 61/576,050, which was filed
in the U.S. Patent and Trademark Office on Dec. 15, 2011, and under 35
U.S.C. §119(a) to Korean Patent Application Serial No.
10-2012-0109999, which was filed in the Korean Intellectual Property
Office on Oct. 4, 2012, the entire disclosure of each of which is
incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to a method and a
transmitter for transmitting wireless power.

[0004] 2. Description of the Related Art

[0005] Recently, wireless or non-contact charging technologies have been
developed, which are now widely used for a variety of electronic devices,
such as wireless electric toothbrushes or wireless electric shavers.

[0006] Using wireless charging technology, which is based on wireless
power transmission and reception, a battery of an electronic device, such
as a mobile phone, may be automatically recharged if, for example, a user
simply places the mobile phone on a charging pad, without connecting a
separate charging connector to the mobile phone.

[0007] Wireless charging technologies may be roughly classified into a
coil-based electromagnetic induction scheme, a resonant scheme, and a
Radio Frequency (RF)/microwave radiation scheme, which delivers
electrical energy by converting it into microwaves.

[0008] Although the electromagnetic induction scheme has been used more
often, recently, experiments using an RF/microwave radiation scheme have
been successful. Thus, it is expected that in the near future, more types
of electronic products will be recharged wirelessly.

[0009] The electromagnetic induction-based power transmission transmits
power between a primary coil and a secondary coil. For example, an
induced current occurs, when a magnet is moved around a coil. Using this
principle, a transmitter generates a magnetic field, and in a receiver, a
current is induced depending on a change in magnetic field, thereby
producing energy. This power transmission method has excellent energy
transmission efficiency.

[0010] As for the resonant scheme, power can be wirelessly transferred to
an electronic device by using the Coupled Mode Theory, even though the
electronic device is located several meters away from a charging device.
The resonant scheme is based on a physics concept, wherein if a tuning
fork rings, a nearby wine glass may also ring at the same frequency.
However, the resonant scheme resonates electromagnetic waves containing
electrical energy, instead of resonating sounds. The resonated electrical
energy is directly delivered only to devices having the same resonant
frequency, and any unused portion is reabsorbed as electromagnetic
fields, instead of being spread into the air. Thus, unlike other
electromagnetic waves, the resonated electrical energy should not affect
adjacent devices and a human body.

[0011] Although wireless charging schemes are garnering a great deal of
attention and research, no standard has been proposed for the priority of
wireless charging, a search for a wireless power transmitter and
receiver, a selection of a communication frequency between the wireless
power transmitter and receiver, an adjustment of wireless power, a
selection of matching circuits, and a distribution of communication time
for each wireless power receiver in one charging cycle. In particular,
new technology is required for a wireless power transmitter to determine
a channel with which it will communicate with a wireless power receiver.

SUMMARY OF THE INVENTION

[0012] Accordingly, the present invention is designed to address at least
the problems and/or disadvantages described above and to provide at least
the advantages described below.

[0013] An aspect of the present invention is to provide a standard for an
overall operation of a wireless power transmitter and receiver.

[0014] Another aspect of the present invention is to provide a method and
a wireless power transmitter that selects a communication channel for
transmitting power, while minimizing conflicts with other communications
channels.

[0015] In accordance with an aspect of the present invention, a method is
provided for transmitting wireless power, by a wireless power
transmitter, to at least one wireless power receiver. The method includes
setting, by the wireless power transmitter, a search channel to be used
for communication with the at least one wireless power receiver;
detecting at least one of an energy level and a Received Signal Strength
Indication (RSSI) value of a signal received on the search channel; and
determining whether to designate the search channel as a communication
channel based on the detection results.

[0016] In accordance with another aspect of the present invention, a
wireless power transmitter is provided for transmitting wireless power to
at least one wireless power receiver. The wireless power transmitter
includes a controller that sets a search channel to be used for
communication with the at least one wireless power receiver; and a
communication unit that receives a signal on the search channel. The
controller detects at least one of an energy level and a Received Signal
Strength Indication (RSSI) value of the received signal, and determines
whether to designate the search channel as a communication channel, based
on the detection results.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other aspects, features, and advantages of certain
embodiments of the present invention will be more apparent from the
following description taken in conjunction with the accompanying
drawings, in which:

[0018] FIG. 1 illustrates an operation of a wireless charging system
according to an embodiment of the present invention;

[0019] FIG. 2 illustrates a wireless power transmitter and a wireless
power receiver according to an embodiment of the present invention;

[0020] FIG. 3A is a flowchart illustrating a channel selection process in
a wireless power transmitter according to an embodiment of the present
invention;

[0021] FIG. 3B illustrates a comparison in available frequency between a
wireless power receiver and a Wi-Fi communication scheme;

[0022] FIG. 3C illustrates a search order by a wireless power transmitter;

[0023] FIG. 4 illustrates a wireless power transmitter according to an
embodiment of the present invention;

[0024] FIG. 5 is a timing diagram illustrating a channel decision process
according to an embodiment of the present invention;

[0025] FIGS. 6A and 6B are flowcharts illustrating a channel decision
process according to different embodiments of the present invention;

[0026] FIG. 7 illustrates a channel search result table according to an
embodiment of the present invention;

[0027] FIGS. 8A and 8B are flowcharts illustrating a communication channel
decision process according to different embodiments of the present
invention;

[0028] FIG. 9A illustrates a network system according to an embodiment of
the present invention; and

[0029]FIG. 9B illustrates execution results of a network system according
to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0030] Various embodiments of the present invention will now be described
in detail with reference to the accompanying drawings. In the following
description, specific details such as detailed configuration and
components are merely provided to assist the overall understanding of
certain embodiments of the present invention. Therefore, it should be
apparent to those skilled in the art that various changes and
modifications of the embodiments described herein can be made without
departing from the scope and spirit of the invention. In addition,
descriptions of well-known functions and constructions are omitted for
clarity and conciseness.

[0031] FIG. 1 illustrates an overall operation of a wireless charging
system according to an embodiment of the present invention.

[0032] Referring to FIG. 1, the wireless charging system includes a
wireless power transmitter 100 and wireless power receivers 110-1, 110-2
and 110-n. The wireless power transmitter 100 wirelessly transmits power
1-1, 1-2, and 1-n to the wireless power receivers 110-1, 110-2, and
110-n, respectively. More specifically, the wireless power transmitter
100 wirelessly transmits powers 1-1, 1-2, and 1-n only to the wireless
power receivers that are authorized by performing a predetermined
authentication procedure.

[0033] The wireless power transmitter 100 forms electrical connections
with the wireless power receivers 110-1, 110-2, and 110-n. For example,
the wireless power transmitter 100 transmits wireless power in the form
of an electromagnetic wave to the wireless power receivers 110-1, 110-2,
and 110-n.

[0034] Additionally, the wireless power transmitter 100 performs
bi-directional communication with the wireless power receivers 110-1,
110-2, and 110-n. The wireless power transmitter 100 and the wireless
power receivers 110-1, 110-2, and 110-n process and exchange packets 2-1,
2-2, and 2-n, each packet consisting of predetermined frames. The
wireless power receivers 110-1, 110-2, and 110-n may be implemented as,
for example, mobile communication terminals, a Personal Digital
Assistants (PDAs), a Personal Multimedia Player (PMP), a smart phone,
etc.

[0035] The wireless power transmitter 100 wirelessly supplies power to the
wireless power receivers 110-1, 110-2 and 110-n, e.g., by the resonant
scheme. When the wireless power transmitter 100 uses the resonant scheme,
the distance between the wireless power transmitter 100 and the wireless
power receivers 110-1, 110-2, and 110-n may be preferably 30 m or less.
However, when the wireless power transmitter 100 uses the electromagnetic
induction scheme, the distance between the wireless power transmitter 100
and the wireless power receivers 110-1, 110-2, and 110-n may be
preferably 10 cm or less.

[0036] The wireless power receivers 110-1, 110-2, and 110-n charge a
battery mounted therein by receiving wireless power from the wireless
power transmitter 100. Further, the wireless power receivers 110-1,
110-2, and 110-n may transmit, to the wireless power transmitter 100, a
signal requesting the transmission of the wireless power, information for
receiving the wireless power, status information of the wireless power
receiver, control information for the wireless power transmitter 100,
etc.

[0037] The wireless power receivers 110-1, 110-2, and 110-n may send a
message indicating their charging status to the wireless power
transmitter 100.

[0038] The wireless power transmitter 100 may include a display that
displays a status of each of the wireless power receivers 110-1, 110-2,
and 110-n based on the messages received from the wireless power
receivers 110-1, 110-2, and 110-n. In addition, the wireless power
transmitter 100 may display an estimated time remaining until the
wireless power receivers 110-1, 110-2, and 110-n will be fully charged.

[0039] Further, the wireless power transmitter 100 may transmit a control
signal for disabling the wireless charging function of the wireless power
receivers 110-1, 110-2, and 110-n. Basically, upon receiving the disable
control signal for the wireless charging function from the wireless power
transmitter 100, a wireless power receiver will disable the wireless
charging function.

[0040] FIG. 2 illustrates a wireless power transmitter and a wireless
power receiver according to an embodiment of the present invention.

[0041] Referring to FIG. 2, a wireless power transmitter 200 includes a
power transmitter 211, a controller 212, and a communication unit 213. A
wireless power receiver 250 includes a power receiver 251, a controller
252, and a communication unit 253. Herein, the term unit refers to a
hardware device or a combination of hardware and software.

[0042] The power transmitter 211 wirelessly supplies the power to the
wireless power receiver 250 via the power receiver 250. The power
transmitter 211 supplies power in an Alternating Current (AC) waveform.
However, when the power transmitter 211 receives its power as a Direct
Current (DC) waveform, e.g., from a battery, the power transmitter 211
supplies the power as an AC waveform, after converting the DC waveform
into an AC waveform using an inverter. The power transmitter 211 may be
implemented as a built-in battery, or may be implemented as a power
receiving interface, which receives power from an outside source, e.g.,
an outlet, and supplies it to other components. It will be understood by
those of ordinary skill in the art that the power transmitter 211 has no
limit as long as it is capable of supplying power in an AC waveform.

[0043] Additionally, the power transmitter 211 may provide AC waveforms to
the wireless power receiver 250 in the form of an electromagnetic wave.
Accordingly, the power transmitter 211 may also include an additional
loop coil, so that it may transmit or receive predetermined
electromagnetic waves. When the power transmitter 211 is implemented with
a loop coil, an inductance L of the loop coil is subject to change. It
will be understood by those of ordinary skill in the art that the power
transmitter 211 has no limit as long as it is capable of transmitting and
receiving electromagnetic waves.

[0044] The controller 212 controls the overall operation of the wireless
power transmitter 200, e.g., using an algorithm, program, or application,
which is read out from a memory (not shown). The controller 212 may be
implemented as a Central Processing Unit (CPU), a microprocessor, a
minicomputer, etc.

[0046] The communication unit 213 transmits signals associated with
information about the wireless power transmitter 200. For example, the
communication unit 213 may unicast, multicast, or broadcast the signals.

[0047] Table 1 below shows a frame structure of a notice signal
transmitted from the wireless power transmitter 200, e.g., at stated
periods, according to an embodiment of the present invention.

[0048] In Table 1, the `frame type` field, which indicates a type of the
signal, indicates that the signal is a notice signal. Further, the
`protocol version` field, which indicates a type of a communication
protocol, is allocated, e.g., 4 bits, and the `sequence number` field,
which indicates a sequential order of the signal, is allocated, e.g., 1
byte. The sequence number increases, e.g., in response to a
transmission/reception step of the signal.

[0049] The `network ID` field, which indicates a network ID of the
wireless power transmitter 200, is allocated, e.g., 1 byte, and the `Rx
to Report (schedule mask)` field, which indicates wireless power
receivers that will report to the wireless power transmitter 200, is
allocated, e.g., 1 byte.

[0050] Table 2 below shows an example of the `Rx to Report (schedule
mask)` field according to an embodiment of the present invention.

[0051] In Table 2, Rx1 to Rx8 correspond to first to eighth wireless power
receivers, respectively. Based on Table 2, a wireless power receiver
whose schedule mask number is represented as `1`, i.e., Rx6, Rx7, and
Rx8, may make a report.

[0052] In Table 1, the `Reserved` field, which is reserved for its future
use, is allocated, e.g., 5 bits, and the `Number of Rx` field, which
indicates the number of wireless power receivers adjacent to the wireless
power transmitter 200, is allocated, e.g., 3 bits.

[0053] The signal in the form of the frame in Table 1 may be implemented
such that it is allocated to Wireless Power Transmission (WPT) in the
IEEE 802.15.4 frame structure.

[0054] Table 3 shows the IEEE 802.15.4 frame structure.

TABLE-US-00003
TABLE 3
Preamble SFD Frame Length WPT CRC16

[0055] As shown in Table 3, the IEEE 802.15.4 frame structure includes
`Preamble`, `Start Frame Delimiter (SFD)`, `Frame Length`, `WPT`, and
`Cyclic Redundancy Check (CRC)16` fields. The frame structure shown in
Table 1 may be included in the WPT field of Table 3.

[0056] The communication unit 213 receives power information from the
wireless power receiver 250. The power information may include at least
one of a capacity of the wireless power receiver 250, a battery level, a
charging count, usage, a battery capacity, and a battery ratio. The
communication unit 213 transmits a charging function control signal for
controlling the charging function of the wireless power receiver 250. For
example, the charging function control signal may enable or disable the
charging function by controlling the power receiver 251 in the specific
wireless power receiver 250.

[0057] The communication unit 213 also receives signals other wireless
power transmitters (not shown). For example, the communication unit 213
may receive a notice signal in the form of Table 1 from another wireless
power transmitter.

[0058] The controller 212 may determine a channel it will use for
communicating with the wireless power receiver 250, based on the signal
from another wireless power transmitter (not shown), which is received
from the communication unit 213. For example, the controller 212 may
determine a channel it will use for communicating, based on a Received
Signal Strength Indication (RSSI) or an energy level of a signal from
another wireless power transmitter. In particular, the controller 212 may
determine a channel that avoids conflicts with another wireless power
transmitter or with other communications channels, such as a Wi-Fi
channel.

[0059] Although FIG. 2 illustrates the power transmitter 211 and the
communication unit 213 in different hardware structures, the power
transmitter 211 and the communication unit 213 may be configured in a
single hardware structure.

[0060] FIG. 3A is a flowchart illustrating a channel selection process in
a wireless power transmitter according to an embodiment of the present
invention.

[0062] In step S303, the wireless power transmitter scans an RSSI of a
received signal (e.g., a notice signal) that is periodically transmitted
from another wireless power transmitter.

[0063] In step S305, the wireless power transmitter selects a
communication channel that will avoid conflicts with a channel used by
another wireless power transmitter or a channel used by other
communications, based on at least one of the ED level scanning result and
the RSSI scanning result. For example, the wireless power transmitter
determines a communication channel by measuring or scanning an ED level
and an RSSI for each channel.

[0064] For example, the wireless power transmitter determines a searched
channel whose energy level or RSSI scanning result is a minimum, as a
communication channel. Particularly, in accordance with an embodiment of
the present invention, the wireless power transmitter scans an energy
level for a frequency in a relatively wide range, based on the Quadrature
Phase Shift Keying (QPSK) modulation scheme. In addition, as the energy
level is scanned, a communication channel may be efficiently determined
regardless of modulation.

[0065] If an ED level input from a specific channel is greater than or
equal to a predetermined threshold, the wireless power transmitter may
not use the channel as a communication channel. In addition, if an RSSI
of a signal received from a specific channel is greater than or equal to
a predetermined threshold, the wireless power transmitter may not use the
channel as a communication channel.

[0066] Alternatively, the wireless power transmitter may perform
communication based on the IEEE 802.15.4 standard, which has channels 11
to 26. A relationship between channels and frequencies in the IEEE
802.15.4 standard is as shown in Table 4 below. A frequency unit in Table
4 is kHZ.

[0067] The wireless power transmitter performs the ED level scanning and
the RSSI scanning in order of channel 11, channel 24, channel 15, and
channel 20.

[0068] More recent wireless power receivers (e.g., smart phones) include a
Wi-Fi communication module, in addition to a communication module for
communication with the wireless power transmitter.

[0069] FIG. 3B illustrates comparisons in available frequency between a
wireless power receiver and a Wi-Fi communication scheme. Specifically,
the upper graph of FIG. 3B is for the IEEE 802.15.4 standard that uses
the frequencies and channels as defined in Table 4. Further, the lower
graph of FIG. 3B is for the frequencies used in Wi-Fi, e.g., IEEE
802.11® 2007.

[0070] Referring to FIG. 3B, a Wi-Fi channel #1 311 uses frequencies of
about 2402 to 2422 kHz, a Wi-Fi channel #6 312 uses frequencies of about
2427 to 2447 kHz, and a Wi-Fi channel #11 313 uses frequencies of about
2452 to 2472 kHz. Therefore, the IEEE 802.15.4 channels, which do not
correspond (321 and 322) to available Wi-Fi frequencies or which
correspond to high-level Wi-Fi signals, may be channels 11, 15, 20 and
24. Accordingly, the wireless power transmitter may perform at least one
of ED level scanning and RSSI scanning for channels 11, 15, 20 and 24.

[0071] Channel 26 may be excluded by U.S. regulations.

[0072] Further, the wireless power transmitter may scan ED values or RSSIs
with respect to channel 11 or 24 first, because channel 11 or 24 is an
interference-minimized channel, as it is positioned at the end of the
Wi-Fi channels.

[0073] FIG. 3C illustrates a search order by a wireless power transmitter.

[0075] In accordance with an embodiment of the present invention, the
channel search order may be determined in such a manner that the wireless
power transmitter first searches for channel #11 331 and then searches
for channel #24 332, which is the farthest channel from the previously
searched channel.

[0076] Additionally, the first searched channel may be determined at
random.

[0077] As described above, the wireless power transmitter determines, as a
communication channel, a channel that minimizes conflicts with other
communications or with a communication channel used by another wireless
power transmitter. In particular, the wireless power transmitter uses
channels 11, 15, 20, and 24 from among the 16 channels defined in the
IEEE 802.15.4 standard.

[0078] FIG. 4 illustrates a wireless power transmitter according to an
embodiment of the present invention.

[0079] Referring to FIG. 4, the wireless power transmitter 400 includes a
DC power supply 410, an inverter 420, a signal matcher 430, a wireless
power transmission unit 440, a controller 450, a communication unit 460,
and a display 470.

[0080] The DC power supply 410 provides power in the form of a DC waveform
that will be supplied to a wireless power receiver. For example, the DC
power supply 410 may be implemented as a battery, or may be implemented
as a device that supplies DC power by converting AC power received from
an outside, e.g., an outlet, into DC power. A voltage Vdd applied to the
DC power supply 410 may be changed under control of the controller 450.

[0081] The inverter 420 converts the DC power received from the DC power
supply 410 into AC waveforms. A power frequency fs and a duty cycle τ
of the inverter 420 may be changed under control of the controller 450.

[0082] The signal matcher 430 performs impedance matching between the AC
power output from the inverter 420 and the wireless power transmission
unit 440.

[0083] The wireless power transmission unit 440 transmits the
impedance-matched AC power to the wireless power receiver in the form of
an electromagnetic wave.

[0084] The communication unit 460 receives power information including
power management information for each wireless power receiver and control
information for the wireless power supply 400, from at least one wireless
power receiver. For example, the communication unit 460 may periodically
transmit a notice signal including a network ID of the wireless power
transmitter 400 to a specific receiving target or may freely broadcast
the notice signal all targets in a broadcast area.

[0085] Additionally, the communication unit 460 may receive a notice
signal from another wireless power receiver and may transmit and receive
specific signals while changing or switching channels. Transmit/receive
channels of the communication unit 460 are determined by the controller
450, as described above with reference to FIGS. 3A and 3B.

[0086] The communication unit 460 detects the energy input from the
surrounding ED and may receive a notice signal from another wireless
power transmitter. The controller 450 determines an RSSI of the notice
signal.

[0087] The controller 450 adjusts the transmit power by analyzing the
power information received from the communication unit 460. In addition,
the controller 450 may determine the channel used by the communication
unit 460 based on the network ID of another wireless power transmitter,
the ED, the RSSI, etc. Further, the controller 450 may generate a network
ID of the wireless power transmitter 400.

[0088] The display 470, e.g., a Liquid Crystal Display (LCD) panel, a
Light Emitting Diode (LED) array, etc., outputs input graphic data to a
user. For example, the display 470 displays indicators for the wireless
power receivers, indicating whether the wireless power receivers are set
to receive or not receive power, an identifier of each of the wireless
power receiver and its associated charging status, and the channel
information used by the wireless power transmitter 400.

[0089] FIG. 5 is a timing diagram illustrating a channel decision process
according to an embodiment of the present invention. Specifically. FIG. 5
illustrates the channel decision process between a controller (or TX MCU)
501, a communication unit (or TX RF) 502 of a wireless power transmitter,
other wireless power transmitters 503 and 504 using a first channel, and
another wireless power transmitter 505 using a second channel.

[0090] Referring to FIG. 5, a user 500 powers up the controller 501 of the
wireless power transmitter in step S511. The controller 501 of the
wireless power transmitter initializes the communication unit 502 of the
wireless power transmitter and sets a channel in step S512. More
specifically, the controller 501 determines a channel to be searched as
an initial search channel, for example, channel 11, as defined in the
IEEE 802.15.4 standard.

[0091] The other wireless power transmitters 503 and 504 that use the
first channel, e.g., channel 11, may periodically transmit a notice
signal in steps S513 and S515. For example, the notice signal transmitted
by the other wireless power transmitters 503 and 504 may have the frame
structure shown in Table 1, and network ID information of each wireless
power transmitter may be included in a network ID field of the notice
signal.

[0092] For example, the other wireless power transmitter 503 has a network
ID of `A`, and the other wireless power transmitter 504 has a network ID
of `B`. In step S513, the wireless power transmitter 503 transmits a
notice signal to the communication unit 502 of the wireless power
transmitter, with network ID information of `A` included in the network
ID field. In step S515, the wireless power transmitter 504 transmits a
notice signal to the communication unit 502 of the wireless power
transmitter, with network ID information of `B` included in the network
ID field. The controller 501 of the wireless power transmitter determines
that the other wireless power transmitters 503 and 504 have the network
IDs of `A` and `B`, respectively, by analyzing the notice signals in
steps S514 and S516.

[0093] The controller 501 decides whether to determine a channel in step
S517. The controller 501 may determine an RSSI of each of the notice
signals received from the other wireless power transmitters 503 and 504,
or an RSSI of an interference signal, or may determine a level of energy
input to the first channel. The controller 501 may decide whether to
determine a channel, based on at least one of the RSSI value and the
energy level value. That is, the controller 501 may decide whether to
determine the first channel as a communication channel. In FIG. 5, the
controller 501 does not determine the first channel as a communication
channel in step S517.

[0094] Accordingly, in step S518, the controller 501 controls the
communication unit 502 of the wireless power transmitter to change the
search channel. Under control of the controller 501, the communication
unit 502 changes the search channel from the first channel to a second
channel. For example, the second channel may be channel 24, as defined in
the IEEE 802.15.4® standard. Alternatively, the controller 501 may
change the searched channel based on a predetermined order as illustrated
in FIG. 3C.

[0095] The other wireless power transmitter 505 using the second channel
has a network ID of `C`. The other wireless power transmitter 505
transmits a notice signal with network ID information of `C` included in
a network ID field in step S519. The controller 501 determines that the
other wireless power transmitter 505 has a network ID of `C`, by
analyzing the notice signal in step S520. The controller 501 of the
wireless power transmitter then decides whether to determine the second
channel as a communication channel in step S521. In FIG. 5, the
controller 501 determines the second channel as a communication channel
in step S521.

[0096] In step S522, the controller determines the second channel as a
communication channel, generates a network ID of the wireless power
transmitter, and determines whether the generated network ID is
duplicated (Duplicated Address Detection (DAD)). The network ID may be
used in a star network for the wireless power system.

[0097] In addition, the controller 501 determines whether the generated
network ID is a duplicate of a network ID of another wireless power
transmitter, i.e., if the network ID is already being used. Determining
whether a network ID is duplicated will be referred to herein as `DAD`.
If the network ID of the wireless power transmitter is a duplicate of a
network ID of another wireless power transmitter, a new network ID may be
re-generated. For example, the controller 501 generates a network ID of
`D` as the new network ID.

[0098] The controller 501 generates a notice signal with the network ID of
`D` included in the network ID field, in steps S523 and S525. In
addition, the controller 501 controls the communication unit 502 to
transmit the notice signal to the other wireless power transmitter 505
that uses the second channel, in steps S524 and S526. For example, the
communication unit 502 periodically broadcasts the notice signal.

[0099] The communication unit 502 receives notice signals from the other
wireless power transmitters 503 and 504 that use another channel, e.g.,
the first channel. The communication unit 502 of the wireless power
transmitter may wait to receive a notice signal on the channel for at
least three cycles, under control of the controller 501. That is, the
communication unit 502 of the wireless power transmitter may wait on the
channel for at least three cycles, even though it fails to receive a
notice signal from another wireless power transmitter.

[0100] FIGS. 6A and 6B are flowcharts illustrating a channel decision
process according to different embodiments of the present invention.

[0101] Referring to FIG. 6A, the wireless power transmitter initializes
the search channel, upon power up, in step S601. The wireless power
transmitter determines an initial search channel and scans at least one
of an RSSI and an energy level of the search channel in step S603. The
wireless power transmitter may determine at least one of an RSSI and an
energy level of a search channel, as a criterion for determining a
communication channel.

[0102] In step S605, the wireless power transmitter determines whether at
least one of the RSSI and the energy level of the search channel is less
than a predetermined threshold. If at least one of the RSSI and the
energy level of the search channel is greater than or equal to the
threshold, the channel is crowded by another wireless power transmitter
or by other communications and should not be used. Accordingly, the
wireless power transmitter fixes (determines) the search channel as a
communication channel to be used for communication in step S613, if at
least one of the RSSI and the energy level of the search channel is less
than the threshold (Yes in step S605).

[0103] However, if at least one of the RSSI and the energy level of the
search channel is greater than or equal to the threshold (No in step
S605), the wireless power transmitter determine whether it has performed
RSSI and ED level scanning for all channels in step S607. For example,
the wireless power transmitter may determine whether it has searched for
or scanned all of the IEEE 802.15.4 channels 11, 24, 15 and 20.

[0104] If the wireless power transmitter has not performed the scanning
for all channels yet (No in step S607), the wireless power transmitter
shifts the search channel in step S609. For example, if the initial
search channel is the IEEE 802.15.4 channel 11, the wireless power
transmitter may change or switch the search channel to the IEEE 802.15.4
channel 24. The wireless power transmitter may change the search channel
based on, for example, a predetermined order as illustrated in FIG. 3C.

[0105] However, if the wireless power transmitter has fully performed the
scanning for all channels (Yes in step S607), the wireless power
transmitter increases the threshold in step S611. Basically, if the
wireless power transmitter fails to determine a communication channel,
even after performing the scanning for all channels, the wireless power
transmitter may increase the threshold, determining that the threshold is
set relatively lower.

[0106] If a communication channel is determined and fixed through the
above process in step S613, the wireless power transmitter generates a
network ID in step S615. In addition, the wireless power transmitter
performs DAD in step S617 to determine whether the generated network ID
is a duplicate of an already used network ID. If the network ID is
duplicated (Yes in step S617), the wireless power transmitter may
re-generate a network ID, i.e., generate a new network ID. If the network
ID is not duplicated (No in step S617), the wireless power transmitter
starts the network in step S619. For example, upon the network startup,
the wireless power transmitter transmits a notice signal.

[0107] As described above, in accordance with an embodiment of the present
invention, the wireless power transmitter immediately determines a
channel as a communication channel, without scanning all of the channels,
once a channel satisfying predetermined conditions is scanned.

[0108] In contrast to the embodiment illustrated in FIG. 6A, FIG. 6B
illustrates an embodiment that scans all of the channels.

[0109] Referring to FIG. 6B, the wireless power transmitter initializes
the search channel, upon power up, in step S601, and determines an
initial search channel and scans at least one of an RSSI and an energy
level of the search channel in step S603. The wireless power transmitter
may determine at least one of an RSSI and an energy level of a search
channel, as a criterion for determining a communication channel.

[0110] The wireless power transmitter updates a channel search result
table by recording the search results in step S625. In step S627, the
wireless power transmitter determine whether the channel search result
table has been completed, as the search is performed for all channels. If
the channel search result table has not been completed (No in step S627),
i.e., if the search has not been performed for all channels, the wireless
power transmitter shifts the search channel in step S629. The wireless
power transmitter may scan at least one of an RSSI and an energy level
for the shifted search channel.

[0111] If the channel search result table has been completed by the above
process (Yes in step S627), the wireless power transmitter determines and
fixes a communication channel in step S631. For example, the wireless
power transmitter determines a channel with a lowest RSSI value or a
lowest energy level as a communication channel. That is, the wireless
power transmitter determines a communication channel by setting any one
of the RSSI value and the energy level as a criterion. Also, the wireless
power transmitter determines a communication channel using both the RSSI
value and the energy level. Alternatively, the wireless power transmitter
may determine a communication channel by analyzing an RSSI to determine
the number of wireless power transmitters that use the relevant channel.

[0112] Once the communication channel is determined and fixed in step
S631, the wireless power transmitter generates a network ID in step S615,
performs DAD in step 617, and performs network startup in step S619.

[0113] As described above for FIGS. 6A and 6B, in determining a
communication channel, the wireless power transmitter may scan either all
channels or some channels.

[0114] FIG. 7 illustrates a channel search result table according to an
embodiment of the present invention. The channel search result table
includes data for a channel number, an address, an RSSI, and a noise
level (i.e., an ED level) for each channel.

[0115] FIGS. 8A and 8B are flowcharts illustrating a communication channel
decision process according to different embodiments of the present
invention. In the examples of FIGS. 8A and 8B, it is assumed that the
wireless power transmitter determines a communication channel based on a
number of other wireless power transmitters that use a search channel,
and on energy levels of signals from the other wireless power
transmitters. In particular, in FIGS. 8A and 8B, the wireless power
transmitter determines, as a criterion, the number of other wireless
power transmitters that use the search channel, rather than the energy
level.

[0116] Referring to FIG. 8A, the wireless power transmitter initializes a
search channel in step S801. The wireless power transmitter scans an RSSI
of the initial search channel in step S803, and determines the number of
other wireless power transmitters that use the search channel, based on
the scanning results.

[0117] In step S805, the wireless power transmitter determines whether the
number of other wireless power transmitters that use the search channel
is less than a predetermined threshold, e.g., 3. If the number of other
wireless power transmitters that use the search channel is less than the
threshold (Yes in step S805), the wireless power transmitter determines
and fixes the search channel as a communication channel in step S821.

[0118] However, if the number of other wireless power transmitters that
use the search channel is greater than or equal to the threshold (No in
step S805), the wireless power transmitter determines whether it has
performed the search for all channels in step S807.

[0119] If the wireless power transmitter has not performed the search for
all channels (No in step S807), the wireless power transmitter changes
(shifts) the search channel to another channel in step S809. For example,
the wireless power transmitter may change the search channel based on a
predetermined order as illustrated in FIG. 3C.

[0120] However, if the wireless power transmitter has performed the search
for all channels (Yes in step S807), the wireless power transmitter scans
an energy level in step S811. The wireless power transmitter may scan an
energy level of the ongoing search channel, or may scan an energy level
by initializing the search channel.

[0121] In step S813, the wireless power transmitter determines whether the
energy level of the search channel is less than a predetermined
threshold. If the energy level of the search channel is less than the
threshold (Yes in step S813), the wireless power transmitter determines
and fixes the search channel as a communication channel in step S821.

[0122] However, if the energy level of the search channel is greater than
or equal to the threshold (No in step S813), the wireless power
transmitter determines whether it has performed the search for all
channels in step S815.

[0123] If the wireless power transmitter has not performed the search for
all channels yet (No in step S815), the wireless power transmitter
changes the search channel to another channel in step S817. For example,
the wireless power transmitter may change the search channel based on a
predetermined order as illustrated in FIG. 3C.

[0124] However, if the wireless power transmitter has performed the search
for all channels (Yes in step S815), the wireless power transmitter
increases the threshold in step S819 and repeats the above-described
process.

[0125] In an alternative embodiment, if the wireless power transmitter has
not performed the search for all channels yet (No in step S807), the
wireless power transmitter may increase the threshold.

[0126] As described above, the wireless power transmitter may determine
the communication channel on which it will perform communication, and may
generate a unique network ID.

[0127] FIG. 8B is a flowchart illustrating a control method in a wireless
power transmitter according to an embodiment of the present invention.

[0128] Referring to FIG. 8B, the wireless power transmitter completes a
channel search result table by scanning an energy level and an RSSI value
for all channels in step S831. The wireless power transmitter determines
the number of other wireless power transmitters that use each channel,
based on the RSSI value in the channel search result table.

[0129] If there is a channel for which the number of other wireless power
transmitters that use the channel is a minimum (Yes in step S833), the
wireless power transmitter determines the channel as a communication
channel in step S835. However, if there are multiple channels for which
the number of other wireless power transmitters that use the channels is
a minimum (No in step S833), the wireless power transmitter determines a
channel with the lowest energy level among the channels, as a
communication channel in step S837.

[0130] FIG. 9A illustrates a network system according to an embodiment of
the present invention.

[0131] Referring to FIG. 9A, the network system 900 includes a wireless
power transmitter 910, a wireless power receiver 920, and a Wi-Fi
repeater 930. The wireless power receiver 920 includes a Wi-Fi
communication module 921 and a wireless charging communication module
922. The Wi-Fi communication may use, for example, a 100 Mbps UDP packet
transmission scheme, and the wireless charging communication may use, for
example, a 250 kbps packet transmission scheme at a frequency of an IEEE
802.15.4 channel 24.

[0132]FIG. 9B is a table illustrating execution results from a network
system according to an embodiment of the present invention. Specifically,
FIG. 9B illustrates execution results in an ordinary office environment.

[0133] Referring to FIG. 9B, a transmitting failure count is 3034 and 6193
when there is no wireless power receiver and when there are five wireless
power receivers, respectively, and the associated failure rates are
0.002337% and 0.004546%, respectively. Based on these results, a channel
decision scheme by the present invention may acquire the excellent
communication results. In addition, it should be understood that the
wireless charging communication does not affect Wi-Fi communication.

[0134] As is apparent from the foregoing description, various embodiments
of the present invention provide a configuration in which a wireless
power transmitter selects a channel for communicating with a wireless
power receiver, while minimizing conflicts with other communications
channels. Particularly, in the a current communication environment in
which Wi-Fi repeaters are widely installed, the wireless power
transmitter may select a communication channel, while minimizing
conflicts with Wi-Fi channels.

[0135] While the present invention has been shown and described with
reference to certain embodiments thereof, it will be understood by those
skilled in the art that various changes in form and details may be made
therein without departing from the spirit and scope of the present
invention as defined by the appended claims and their equivalents.